Methods and devices for active vibration damping of an optical structure

ABSTRACT

A vibration damper assembly that may be attached and moved about a payload or optical mount surface of an optical structure such as an optical table. The vibration damper assembly may include a sensor and an actuator that may be disposed within a housing. In some embodiments, the vibration damper assembly or components thereof may be incorporated into an optical structure in the form of an optical component to be disposed or mounted on an optical mount surface of an optical structure such as an optical table. Embodiments of the vibration damper system may include a controller in communication with the damper assembly Embodiments of the controller may use adaptive tuning, auto-ranging selection of gain factors and other features in order to optimize damping performance.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. section 119(e) fromcopending U.S. Provisional Patent Application Ser. No. 60/634,227,entitled “Method and Apparatus for Active Vibration Dampening of anOptical Structure or Substrate”, filed December 7, 2004, by V. Ryaboy,P. Kasturi and A. Nastase, which is hereby incorporated by referenceherein in its entirety. This application is related to commonly ownedco-pending U.S. patent application Ser. No. 10/693,222, entitled“Instrumented Platform for Vibration-Sensitive Equipment” filed Oct. 24,2003, by Ryaboy et al., and commonly owned co-pending U.S. patentapplication Ser. No. 10/971,623, entitled “Instrumented Platform forVibration Sensitive Equipment”, filed Oct. 22, 2004, by Ryaboy et al.,both of which are incorporated by reference herein in their entirety.

BACKGROUND

In many experimental research and industrial applications equipment andmethods are used that are adversely affected by vibration. Vibration maybe intrinsically caused by the equipment and methods, or the vibrationmay be transferred to the equipment from the surrounding environment. Assuch, it is desirable in these circumstances to have a low vibrationmount surface and mount components for mounting such sensitiveequipment. One example of an optical structure with an optical mountsurface is an optical table which is typically used for mounting opticalequipment as well as other equipment that is sensitive to vibration. Inorder to reduce vibration transferred to an optical table, most opticaltables are equipped with vibration isolators which reduce vibrationtransmitted to the table from the floor upon which the table rests.

The vibration isolators may be assembled to the table at predeterminedlocations to optimize damping of the vibrational modes of the opticaltable. Often, one or more vibration isolators are positioned between acoupling surface of the optical table and the one or more table supportsor legs, thereby passively limiting the transmission of vibrationalinfluences from the environment to the devices supported on the couplingsurface of the table. Exemplary passive vibration isolators includefluid bladders, springs, shocks, foams, and the like.

An optical table itself, however, has its own natural frequencies andcorresponding flexural vibration modes that can be easily excited byresidual vibration coming through the isolators or by other sources suchas acoustical excitation, air turbulence and dynamic forces generated bythe payload equipment installed on the optical table. The main flexuralvibration modes usually have a global character, which means that anexcitation at any point of the table generates a vibration patternencompassing the whole optical table structure. These natural vibrationsare only very lightly damped, in general, and therefore can reach highamplitudes unless special damping means are introduced into the opticaltable structure. Some special damping means may include passive dampersthat may be specifically tailored to natural frequencies of the opticaltable.

Passive dampers of various designs are widely used in construction ofoptical tables. The “Shock and Vibration Handbook”, ed. By C. M. Harris,4^(th) edition, 1996; 5^(th) edition, 2001, Ch. 37, provides a surveyand a classification of dampers or damping treatments. According to thisreference, known types of damping treatments include free-layer dampingtreatments, where the energy is dissipated by means of extensionaldeformation of a damping layer (made of visco-elastic material) inducedby flexural vibration of the base structure. Also included areconstrained-layer damping treatments, where the constraining layer helpsinduce relatively large shear deformations in the visco-elastic layer inresponse to flexural vibration of the base structure, thereby providingmore effective energy dissipation mechanism. Also included are integraldamping treatments, including use of damped laminated sheets and/ordamped joints in the construction assembly and tuned passive dampers,which are essentially mass-spring systems having resonances which arematched or tuned to one or more resonance frequencies of the basestructure. The application of the tuned damper replaces the resonancepeak of the base structure, typically, by two peaks of lesser amplitude.Finally, damping links, i.e., visco-elastic elements joining two partsof the structure that experience large relative motion in the process ofvibration are disclosed.

However, even with such passive damping equipment installed, an opticaltable or other optical structure may have vibration characteristicsdifferent than an analytical model that was used to tune such dampingequipment. Additionally, differing payload configurations may creatediffering harmonic frequencies as well as differing nodes and anti-nodesin an optical table or other optical structure. Also, there is a growingdemand for high precision and high throughput capabilities in theoptoelectronics and semiconductor industries, as well as similar needsfor modern scientific experimental instruments. These needs requirehigher damping performance of optical structures such as optical tablesand optical components that may be mounted to optical mount surfaces ofthe optical tables.

In light of the foregoing, there is an ongoing need for methods anddevices configured to efficiently reduce vibration in an opticalstructure that arise from a variety of vibration sources. In addition,there is a need for vibration damping capability that may be moved aboutan optical mount surface of an optical structure such as an opticaltable or the like in order to position the damping capability in thelocation where it is needed most. What has also been needed are systemsand methods for applying vibration damping capability directly tooptical components which may be mounted onto an optical mount surface ofan optical structure. Also, there is a need for control systems foractive vibration damper assemblies that are adaptable to payload changeson an optical structure, can accommodate a wide variety of vibrationmagnitude variations, can be easily or automatically tuned and can beincorporated into active vibration damping systems which may be producedat a modest cost.

SUMMARY

In one embodiment, a method of adaptively tuning a controller of anactive vibration damper system includes providing an active vibrationdamper system for an optical structure including at least one activevibration damper assembly. The vibration damper assembly has a vibrationsensor and an actuator. The damper system includes a controller coupledto both the sensor and the actuator by a control channel. Initially, allcontrol channels except one active channel are disabled. In theremaining active control channel, the gain factor of the control channelis increased until instability of the active damper system is detectedby the vibration sensor. The gain factor is then reduced by a smallincrement to re-achieve stability of the active damper system. The gainfactor that achieved stability is then stored. The procedure is thenrepeated for any remaining control channels. Thereafter, all controlchannels are reactivated and gain factors to each control channelincreased in an amount or amounts proportional to the stored gainvalues. The gain factors are proportionally increased for eachrespective channel until instability is again detected by a vibrationsensor. The gain factors are then reduced in small steps for eachcontrol channel until stability is achieved for the vibration dampersystem.

In another embodiment, a method of automatically selecting anappropriate range of input vibration signal detection in an activedamper assembly includes providing an active vibration damper system foran optical structure. The active vibration damper system includes anactive vibration damper assembly having a vibration sensor and anactuator and a controller coupled to both the vibration sensor and theactuator by a control channel. The controller also has at least onevibration feedback signal input with gain factors appropriate to thesignal strength range for the inputs. A vibration feedback signal fromthe vibration sensor is monitored. The vibration feedback signal iscompared to a pre-selected range of signal values over a pre-selectedperiod of time. An appropriate feedback signal range input is selectedwith an gain factor appropriate for the input signal amplitude in thecontroller.

In another embodiment, a method of determining a payload change appliedto an active vibration damper system includes providing an activevibration damper system. The active vibration damper system providedincludes an active damper assembly having a vibration sensor and anactuator and a controller coupled to both the vibration sensor and theactuator by a control channel. The controller also has a vibrationfeedback signal input with gain factor appropriate to the signalstrength range for the vibration signal input. A vibration feedbacksignal is monitored for vibration overload conditions. Upon detection ofa vibration overload condition, the drive signal to the actuator fromthe controller is disabled and a determination is made as to whether thevibration overload condition still exists. If the overload conditionceases when the drive signal to the actuator from the controller isdisabled, a change in payload has occurred.

In one embodiment, an optical component with active vibration dampingincludes a body portion and a mount plate secured to the body portionand configured to be mounted to an optical mount surface. An actuator ismechanically coupled to the body portion. In some embodiments, avibration sensor is also mechanically coupled to the body portion with acontroller in communication with the actuator and vibration sensor. Forsome embodiments, the optical component may include an optical postmount.

These features of embodiments will become more apparent from thefollowing detailed description when taken in conjunction with theaccompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a optical structure in the form of anoptical table;

FIG. 2 is a side sectional view of the optical table;

FIG. 3 is a perspective view of the optical table coupled to a monitorand/or controller;

FIG. 4 is a cross-sectional view of a portion of an embodiment of anoptical table with an active damper assembly in a table core;

FIG. 5 is a schematic of an active vibration damper system including anactive or controllable vibration damper assembly in an optical tablecore;

FIG. 6 is a perspective view of an embodiment of a piezoelectric activedamper assembly;

FIG. 7 is a perspective view showing an active vibration damper systemattached to a payload surface of an optical table embodiment;

FIG. 8 is a cross-sectional view of an embodiment of a vibration damperassembly;

FIG. 9 is a side view of an optical table assembly with a vibrationdamper assembly located between a table of the optical table assemblyand a vibration isolator of the optical table assembly;

FIG. 10 is a perspective view of an optical table or platform thatincludes two vibration damper assembly embodiments coupled to acontroller;

FIG. 11 is an elevation view in partial section of a vibration damperassembly embodiment that is configured to actively damp vibration andincludes a vibration sensor, an actuator, a driver device and a housing;

FIG. 12 is a block diagram illustrating a method of active damping of anoptical table or other low vibration surface or structure;

FIG. 13 is a block diagram illustrating a dual control channel method ofactive vibration damping;

FIG. 14 is a graphical representation of a method of determining gainfactors for a controller of an active vibration damper system utilizingadaptive tuning;

FIGS. 15A-15C illustrate representations of interactive screen displayson a display of an embodiment of a controller.

FIG. 16 is a perspective view of an optical structure which is anoptical component in the form of an optical post having a lens mountdevice at a top of the post and a vibration damper assembly disposedwithin a body portion of the post which is coupled to a controller.

FIG. 17 is an elevational view in partial section of optical componentof FIG. 16.

DETAILED DESCRIPTION

As discussed above, in many experimental research and industrialapplications equipment and methods are used that are adversely affectedby vibration. Vibration may be intrinsically caused by the equipment andmethods, or the vibration may be transferred to the equipment from thesurrounding environment. As such, it is desirable in these circumstancesto use low vibration optical structures that may include optical mountsurfaces and optical components that may be mounted to optical mountsurfaces. Optical mount surfaces may be found on optical structures suchas optical tables, optical benches, optical breadboards, laserplatforms, optical platforms and the like. Optical components mayinclude, without limitation, optical mounts, optical posts, lensholders, lasers, adjustable platforms and the like.

Some embodiments include an active vibration damper assembly that may bedetachably secured to an optical mount surface of an optical structuresuch as an optical table. Such embodiments may be detached and movedabout a surface of an optical table or other optical mount surface to adesired location and then re-attached to the optical mount surface.Other embodiments include a vibration damper assembly that may beincorporated into an optical structure having an optical mount surfacesuch as an optical table. The active vibration damper assemblyembodiment includes at least one sensor and at least one actuator whichmay optionally be located or disposed within a housing. The housing of adetachable embodiment of an active damper assembly may be attached toany surface of the table or work surface. For example, in someembodiments, the vibration damper assembly is configured to be attachedto an optical mount surface of an optical table or platform configuredto support any number of optical components. In some embodiments, thevibration damper assembly may be coupled to an optical mount surface ofan optical table adjacent to one or more optical table supports or legs.In some embodiments, the vibration damper assembly may be coupled to asurface of the optical table in opposition to the one of more opticaltable support structures or legs. The housing may be configured toattach to a surface of an optical table or platform using one or morefasteners. For example, in some embodiments the active vibration damperassembly may be detachably coupled to a surface of an optical table orplatform. As such, an operator can move the active vibration damperassembly to different locations of the table or platform, therebypermitting the operator to optimize the damping function of thevibration damper assembly.

FIGS. 1 and 2 show an optical structure which has an optical mountsurface and which is in the form of a platform 10. The platform 10 mayinclude an optical table 12 that has a first surface 14, a secondsurface 16 and a plurality of side surfaces 18. The first surface 14 mayextend along a first plate 20, the second surface 16 may extend along asecond plate 22 and the side surfaces 18 may extend along one or moreside plates 24.

The first plate 20 is separated from the second plate 22 by an innercore 26. The first plate 20 and second plate 22 of the platform 10 maybe constructed of one or more materials including, without limitation,stainless steel, aluminum, carbon fiber, granite, steel, carbon steel,laminated metals, composite metals, wood, laminated woods, compositewoods, formica, formica covered substrates, fiberglass, compositematerials, Kevlar, cast iron, and the like. The first plate 20 andsecond plate 22 may be manufactured from a like material. In thealternative, the first plate 20 and second plate 22 may be manufacturedfrom different materials.

Like the first and second plates 20, 22, the inner core 26 of theplatform 10 may be manufactured from a variety of materials. Exemplarycore materials include, without limitation, various metals and metalliccomposites including steel, titanium, aluminum, iron; granite; variouswoods and wood composites including medium density fiber board, particleboard, and the like; cardboard, multiple component laminates; compositematerials including carbon fiber, Kevlar, and the like; and similarmaterials. In one embodiment, the inner core 26 may contain a honeycombstructure 28 to provide support for the plates 20 and 22. Optionally,the inner core 26 may be constructed without a honeycomb structure.

Optionally, the first plate 20 and/or the second plate 22 may beconfigured to have any number of mounting features. For example, thefirst plate 20 and/or the second plate 22 may include a plurality ofmounting features in the form of threaded apertures 30 which areconfigured to receive at least a portion of a mounting device of anoptical component or the like such as a threaded bolt or screw withthreads configured to mate with the threaded apertures 30. Optionally,the apertures 30 need not be threaded and the mounting of opticalcomponents or other components to be mounted to an optical mount surfacemay use gravitational forces, magnetic forces or the like. Exemplaryoptical components may include, without limitation, optical mounts,posts, lens supports, isolation supports or platforms, and the like. Inother embodiments, the platform 10 may be configured to support avariety of measuring devices or other vibration-sensitive devicesthereon. For example, the platform 10 may be configured to support amass spectroscopy device, nuclear magnetic resonance (NMR) measuringdevice, crystal growth apparatus or similar vibration-sensitive devicesthereon. In other embodiments, first plate 20 and/or the second plate 22may be configured to have one or more optical components or similardevices magnetically coupled thereto. As such, the first plate 20,second plate 22, or both may be manufactured without apertures 30therein. Optionally, the platform 10 may be configured to have one ormore optical components or devices coupled thereto using any one of anumber of attachment methodologies. Exemplary attachment methodologiesinclude, without limitation, detachably coupled, non-detachably coupled,welded, adhesively coupled, friction coupled, electro-magneticallycoupled, or the like.

Referring again to FIGS. 1 and 2, an external payload 32 that may be avibration-sensitive payload 32 may be attached to one or more threadedapertures 30 of the table 12. The payload 32 may be any type of weightor mass including a device such as an optical component of an opticalsystem, a device under test in a shaker machine, a mass spectroscopydevice, nuclear magnetic resonance (NMR) measuring device, crystalgrowth apparatus etc. Additionally, the table may be a platform forequipment used to fabricate semiconductor wafers, integrated circuits,etc. In general the table 12 may be any platform used to support acomponent, system or equipment used in manufacturing or laboratoryenvironments.

One or more vibration sensors 34 may be located within the inner core 26and attached to an underlying surface 36 of the first plate 20. Thevibration sensors 34 may be any type of device, such as anaccelerometer, a geophone or displacement sensor that can sensevibration. Although three vibration sensors 34 are shown, it is to beunderstood that any number of sensors 34 can be located at any locationof the table. The vibration sensors 34 can be connected to an electricalconnector 38 attached to one of the side plates 24 of the table 12. Thesensor 34 may be connected to the connector 38 by wire cables 40 thatrun through the inner core 26. The sensors 34 may provide an outputsignal that is transmitted to the connector 38 over the cables 40.

As shown in FIG. 3, a monitor and/or controller 42 may be coupled to thesensors 34 by plugging cables 44 into the connector 38. The monitorand/or controller 42 may record and/or display vibration informationprovided by the sensors 34. Optionally, the monitor and/or controller 42may be configured to provide a control signal to an active orcontrollable actuator (not shown) integrated into the table 10.Referring again to FIG. 3, by locating the vibration sensors 34 withinthe inner core 26, the sensors 34 can measure the vibration directlybeneath the external device 32 thereby providing more accurate vibrationdata. The electrical connector 38 allows the controller 42 to be readilycoupled to the sensors 34 thereby minimizing set-up time for monitoringvibration in the table 12. Although cables 40 and a connector 38 areshown and described, it is to be understood that the sensors 34 may havea wireless transmitter (not shown) that wirelessly transmits an outputsignal or signals from the sensors 34 to the monitor and/or controller42.

FIG. 4 shows an embodiment of a table assembly 10′ with a vibrationdamper assembly 50 located within the inner core 26. The active orcontrollable vibration damper assembly 50 may include the sensor 34 andan actuator 52 having an active element 54 in the form of an electriccoil such as a voice coil that can be excited to induce a vibration thatoffsets and cancels the vibration of an optical structure such as thetable 12. The electric coil of the actuator 52 is magnetically coupledto a magnet mass 56. The magnet mass 56 is mechanically coupled to anactuator housing 57 by flexures in the form of a pair of flexiblediaphragms 58. The housing 57 is attached to the plates 20 and 22. Thatdiaphragms 58 function as springs which combine with the mass 56 to forma spring/mass assembly. Providing a current to the coil 54 generates amagnetic force that moves the mass 56. The coil 54 can be excited in amanner to generate, together with the spring/mass assembly, a dynamicforce to offset vibration in the table 12.

The vibration sensor 34 may be coupled to the optical table 12 using avariety of techniques. For example, the vibration sensor 34 may becoupled to the table using a screw 60 that extends through the top plate20 and is attached to a sensor housing 62. The sensor 34 may be coaxialand rigidly coupled to the actuator 52. The sensor 34 provides an outputsignal to a control circuit 64 as shown in FIG. 5. The control circuit64 processes the output signal and provides an excitation signal to thecoil 54 to generate an offsetting vibration that cancels the tablevibration. The control circuit 64 can be located within the inner core26 and connected to the sensor 60 and coil 54 by cables 66.

While certain exemplary embodiments have been described and shown, it isto be understood that such embodiments are merely illustrative of andnot restrictive and various other modifications may be used. Inparticular, optical structures referred to as optical tables or opticalmount surfaces thereof may include any kind of a support structure,including multi-level platforms or cradle platforms. The working oroptical mount surface of these support structures may be horizontal,vertical or even inclined. Accordingly, the line of action of thesensors and active dampers can be vertical, horizontal or inclined andmultidirectional sensor or active damper embodiments are alsocontemplated. Although FIG. 4 shows an actuator 52 that is implementedas an electromagnetic shaker with a moving magnet 56 and a stationarycoil 54, other types of actuator designs can be used, in particular,electromagnetic designs with stationary magnets and moving coils,electrodynamic designs with one stationary and one moving coil, etc.Alternatively, stiff (e.g. piezoelectric) actuators can be employed tocreate a relative motion of the reactive mass and the table.

Active damper assemblies are typically located at fixed positions,normally at the corners of an optical table or the like. Thisarrangement allows for effective reduction of natural vibrations of thetable at its resonance frequencies. It may not, however, be effectivefor reducing forced vibration of the table caused by mechanical oracoustical excitation at a fixed frequency. Even if programmed to createincreased mechanical impedance at this frequency, they may reducevibration only locally at the installation point. In order to addressthis, add-on or detachable controlled vibration damper assemblyembodiments may be installed near the most vibration-sensitivecomponents or near the sources of forced vibration and programmed toreduce vibration at certain fixed frequencies, thereby providingprotection against forced vibrations.

FIG. 5 is a schematic view of an active or controllable vibration damperassembly 50 coupled to a controller 64. A vibration sensor 34 of thevibration damper assembly 50 is integrated into or otherwisemechanically coupled to the table 10′. A signal from the vibrationsensor 34 is transmitted to the controller 64. The controller 64 maycontain amplifiers 75, compensators 76 and filters 77 as well as othercomponents such as a processor (not shown). Digital control, analogcontrol or both may be used to analyze the signal from the vibrationsensors 34 and generate a vibration canceling output signal transmittedto the damper assembly 50. The transformed vibration canceling outputsignal is fed into the active element 54, such as a coil, of theactuator 52 which may be incorporated into or otherwise mechanicallycoupled to the table structure. The vibration actuator coil 54 mayfurther be coupled to the reaction mass 56, which may contain magnets,and the flexure 58 that provides elastic coupling between the mass 56and the tabletop. The amplification gains and other parameters of thecontroller modules of the controller 64 are assigned and coordinatedwith the characteristics of the sensor, actuator and mechanical assemblyso that a force F_(a) induced on the table reduces the vibration at thispoint. As control current flows through the coil 54 of the actuator 52,the electromagnetic force acts on the reaction mass 56, and theequivalent reaction force is acting on the stationary coils or flexure58 fastened to the table structure. The control loop of the controller64 is designed so that the phase and the amplitude of the summary forcetransmitted to the table structure counteract the vibration of the table10′ as measured by the sensor 34.

In one embodiment, the locations represented by points A,B and C in FIG.5 may be co-axial and disposed on the same vertical axis and rigidlyconnected. Optionally, the control loop coupled between sensor 34 andactuator 52 of the active damper assembly 50 may be designed such thatthe active force acting on the table 10′ emulates the effect of aviscous damper in the frequency domain encompassing the main naturalfrequencies of the flexural vibration of the table. This approachcreates inherent stability and robustness with respect to the changes inthe payload 32. To implement this strategy, an embodiment of thetransfer function of the controller 64 may be designed as:${K(\omega)} = \frac{{- {\mathbb{i}}}\quad\omega\quad k}{{A(\omega)}{S(\omega)}}$

Where;

ω=2π f=a circular frequency.

A(ω)=the actuator (shaker) transfer function, or ratio of the totalforce N exerted by the actuator on the structure to input voltage, N/V.

S(ω)=the sensor transfer function, or the ratio of the sensor outputvoltage to the dynamic displacement, V/m.

K(ω)=the controller transfer function, V/V.

k=an adjustable gain.

As a result, the force exerted by the active vibration damper assembly50 on the table structure will equal iωkμ, where μ is the dynamicdisplacement amplitude of the table 10′, which is equivalent to theaction of the viscous damping. Of course, other units can be used. Thesensor 34 may be an accelerometer, a velocimeter (such as a geophone) ora displacement sensor. Additional correcting filters may be used toimprove the stability margins or other parameters.

FIG. 6 shows an alternate embodiment of a portion of an optical table 12wherein a strip 80 is located between the top plate 20 and a holesealing tile 82. The hole sealing tile 82 may have a plurality of cups84 that are located adjacent to the threaded apertures 30 to collectdebris that fall through the apertures 30. The strip 80 may be apiezoelectric device that functions as an active damper assembly with asensor and/or an actuator such as actuator 52 discussed above.Alternatively, optical cables or other devices may be located betweenthe plate 20 and tile 82 to provide sensing and/or actuating functions.The tile 82 can protect the strip 80 during the manufacturing process ofconstructing the table 12.

FIG. 7 shows a pair of vibration damper assemblies 100 that are attachedto the first payload surface 14 of the table 12. The payload surface 14may support a payload such as a pair of optical components or devices102. Each damper assembly 100 can be attached to different locations ofthe payload surface 14 using various device and/or methods. For example,in one embodiment, each damper assembly 100 is secured to the table 12by fasteners 104 screwed into the threaded apertures 30 of the table 12.Optionally, each damper assembly 100 may be coupled to the table 12using any variety of alternative coupling techniques. Exemplaryalternate coupling techniques include, without limitation, welding,adhesively bonding, magnetically coupling, clamping, and the like. Assuch, the damper assembly 100 may be detachably or non-detachablycoupled to the table 12. When detachably coupled to the table 12, theoperator of the table 12 can detach and move each damper assembly 100 toa different location of the payload surface 14 to optimize the dampingfunction of the vibration damper assemblies 100.

The damper assemblies 100 are also coupled or connected to a controller106. The controller 106 may be the same or similar to the controller 64shown in FIG. 5 and described in the accompanying text. Although anexternal controller 106 is shown and described, it is to be understoodthat at least one of the assemblies 100 may be modified to contain oneor more circuits of the controller 106.

FIG. 8 shows an embodiment of the vibration damper assembly 100 inpartial section. The assembly 100 includes a housing 110. The housing110 may include a first compartment 112 that contains a vibration sensor114 and a second compartment 116 that contains an actuator 118 whichincludes an active element, a spring member or flexure and a mass. Thesensor 114 and actuator 118 may be the same as or similar to the sensor34 and actuator 52 including active element 54, spring member diaphragm58 and magnetic mass 56 shown in FIG. 4 and described in theaccompanying text. For example, the actuator 118 may include one or moreactive elements. The first compartment 112 may be sealed by an O-ring120 or other type of seal.

The housing 110 may be constructed from a metal material, such as amagnetic metal material, to isolate the sensor 114 from electromagneticnoise, particularly noise produced by the actuator 118. The housing 110may actually be constructed from an outer shell 122, an inner shell 124and a base 126. The housing components 122, 124 and 126 may be attachedtogether by a plurality of fasteners 128. The actuator 118 may becoupled to the inner shell 124 by a threaded adapter 130 and held inplace by fastener 132.

The base 126 may have an interface plate in the form of a collar 134with a plurality of apertures 136 that provide thru holes for fasteners(see FIG. 7) that attach the vibration damper assembly 100 to a table orother optical structure. Although thru holes are shown and described, itis to be understood that other means may be employed to attach thevibration damper assembly 100 to the table. For example, the base 126may have a plurality of studs that extend from the interface plate 134and can be pressed into the apertures 30 of the table. The damperassembly 100 may include a first electrical connector 138 that isattached to the sensor 114 by a wire(s) 140 and a second electricalconnector 142 that is connected to the actuator 118 by a wire(s) 144.The connectors 138 and 142 can be connected to the electrical circuitsof the controller 106 shown in FIG. 7.

In operation, a vibration damper assembly 100 is attached to the payloadsurface 14 by inserting the fasteners 104 through the interface plateapertures 136 and securing the housing 110 to the table 12. Theconnectors 138 and 142 are connected to the controller 106, although theconnectors 138 and 142 may be connected before attachment of the housing110 to the table 12 or at any other suitable time. Once set up, thevibration sensor 114 senses vibration of the table surface and generatesa signal which is communicated to the controller 106. The controller 106processes the signal and generates a drive signal which is communicatedto the actuator 118. The actuator 118 then converts the drive signalinto vibrational motion of the mass of the actuator 118 where suchvibrational motions is configured to damp the vibration of the table. Anoperator can attach a display or monitor (see FIG. 3) to the vibrationdamper assembly 100 to utilize the sensor 114 to sense and graphicallydisplay vibration at the table location. The operator can move thevibration damper assembly 100 around the table surface or any otheroptical mount surface to sense vibration at different locations of thepayload surface 14 and to optimize damping of the table 12.

FIG. 9 shows an embodiment of a table assembly with a vibration damperassembly 100′ located between an optical table 12 and a vibrationisolator 150. The function of the vibration isolator 150 is primarily toisolate the table 12 from vibration of the floor. The vibration damperassembly 100′ and isolator 150 are in separate housings which allows anoperator to add, or remove the damper assembly 100′ from the tableassembly. The vibration isolator 150 may be of any suitable type knownin the art. The separate damper assembly 100′ provides an operator ofthe table assembly with flexibility in damping vibration in the table12. Although not shown in FIGS. 1, 3 and 7, it is to be understood thatthe table 12 of those figures shown may be supported by the isolator 150or any other structure such as table legs.

FIG. 10 shows an embodiment of an optical structure in the form of anoptical support structure or platform having two active vibration damperdevices or assemblies 220 integral therewith or otherwise coupledthereto. In the illustrated embodiment, the optical support structure210 includes a first surface 212, a second surface 214, and a core 216therebetween. In one embodiment, at least one of the first surface 212and the second surface 214 may be configured to have one or more opticalelements and/components, mounts, and/or measuring devices coupledthereto. For example, in the illustrated embodiment, the first surface212 of the optical support structure 210 includes one or more apertures218 configured to receive and engage at least a portion of an opticalcomponent in the form of an optical mount (not shown). Optionally, thesecond surface 214 and/or the structure body 216 of the optical supportstructure 210 may likewise include one or more apertures 218 formedthereon. In one embodiment, the one or more apertures 218 may besealingly formed within the optical support structure 210 having cupsdisposed about the one or more apertures 218 to prevent leakage ofmaterials or parts into the structure body 216. Further, embodiments ofthe one or more apertures 218 may be threaded and capable of receivingat least one optical component such as an optical mount in threadedrelation therein. Finally, for some embodiments, the one or moreapertures 218 may be numerous and evenly spaced at regular intervals,such as an orthogonal grid of apertures 218 spaced about 0.5 inch toabout 1.5 inches apart.

Referring again to FIG. 10, the first surface 212, the second surface214, and the structure body 216 may be constructed of any variety ofmaterials. For example, at least one of the first surface 212, thesecond surface 214, and the structure body 216 may be constructed of oneor more materials including, without limitation, stainless steel,titanium, iron, cast iron, aluminum, carbon fiber, granite, steel,carbon steel, laminated metals, composite metals, wood, laminated woods,composite woods including medium density fiber board, particle board,cardboard, multiple component laminates, formica, formica coveredsubstrates, fiberglass, composite materials, Kevlar®, and the like. Inone embodiment, the first and second surfaces 212, 214, respectively,may be constructed from stainless steel while the structure body 216 isconstructed from aluminum. Optionally, in one embodiment, the structurebody 216 may be constructed of a honeycomb structure and configured toprovide support for the first and second surfaces 212 and 214.Optionally, the structure body 216 may be constructed without ahoneycomb structure.

As shown in FIG. 10, the vibration damper assemblies 220 may be coupledto or otherwise in communication with at least a portion of the opticalsupport structure 210. In the embodiment shown in FIG. 10, both thedamper assemblies 220 are integrally secured to the optical supportstructure 210. In some embodiments, however, one or more of the damperassemblies 220 may be detachably coupled to any portion of the supportstructure 110, including at least one of the first surface 212, thesecond surface 214, and/or the structure body 216. Any variety or numberof damper assemblies 220 may be secured, coupled or in communicationwith the optical support structure 210, including 1, 2, 3, 4, 5, 6 ormore active vibration damper assemblies 220. The discussion above withregard to FIGS. 1-9 discloses a number of vibration damper devices orassemblies 50, 80 and 100, any combination of which may be used inconjunction with active damper assembly 220 with the optical supportstructure 210.

The damper assemblies 220 may be secured to the support structure 210,or any portion or component thereof, such as at least one of the firstsurface 212, the second surface 214, and/or the structure body 216. Inthe illustrated embodiment, the active damper assemblies 220 arepositioned proximate to the structure body 216 and are in communicationwith the first surface 212 and the second surface 214. In addition, thedamper assemblies 220 are disposed at corners of the optical supportstructure 210 which has a generally rectangular configuration for theembodiment shown. The damper assemblies 220 may, however, be disposed atany desired position on the optical support structure 210.

The damper assemblies 220 may be secured to the optical supportstructure 210 in any variety of ways, including, without limitation,magnetically secured, mechanically secured, screwed, bolted, orotherwise secured thereto with one or more threaded members. The damperassemblies 220 may also be secured to the optical support structure withone or more tracks or attachment devices positioned on the opticalsupport structure 210, using vacuum force, using gravitation force,adhesively secured or bonded, or the like. Exemplary fastening devicesfor securing the damper assemblies 220 to the optical support structure210 include, without limitation, screws, bolts, threaded members,rivets, lock pins, nails, tacks, locking members, and the like.

Referring to FIG. 11, the active vibration damper device or assembly 220may include one or more sensors 240 and one or more vibration actuators242. The vibration actuators 242 may also include one or more activeelements, flexural or spring members and mass members as discussedabove. The sensor 240 may include vibration sensors, accelerometers,geophones, or other sensors. Exemplary actuators for the actuator 242may include, without limitation, electrodynamic devices, electromagneticdevices, piezoelectric devices, and any other suitable actuator. Oneparticular active element of the actuator 242 may include a voice coildevice or the like.

For some embodiments, the sensor 240 and actuator 242 are disposed in aco-axial orientation. In other embodiments, the sensor 240 and actuator242 are not co-axially oriented. Similarly, the sensor 240 and actuator242 may or may not be oriented in a direction perpendicular to at leastone of the first surface 212, the second surface 214, and/or thestructure body 216. The sensor 240 may be coupled to an optional driverdevice 248 disposed adjacent the actuator 242 with at least one conduit244 that is configured to carry information or energy such as anelectrical wire or wires. Similarly, the actuator 242 may be coupled tothe driver device 248 with a similar or other suitable conduit 246.Optionally, the sensor 240 and actuator 242 may be wirelessly coupled tothe driver device 248. The driver device 248 may include a pre-amplifierand be configured to receive a signal or signals from the sensor 240,amplify the signal and communicate the amplified signal to a controller.The driver may also include amplifiers configured to amplify controlsignals from the controller and transmit the amplified signal or signalsgenerated therefrom to the actuator 242.

As shown in FIG. 11, the various elements of the vibration damperassembly 220 may be positioned within a single housing or casing 250.Optionally, the damper assembly 220 may comprise a number of housingsconfigured to be interconnected, thereby providing a modular damperdevice design capable of being configured for specific applications ofusers depending on their needs. For example, a damper assembly 220 mayhave a variety of sensors. In another embodiment, a damper assembly 220having a variety of actuators 242 may be used. As shown in FIG. 11, atleast one connector 252 is in communication with the driver device 248thereby permitting the conduit 222 coupled to the controller 224 (SeeFIG. 10) to be coupled to the driver device 248.

Referring again to FIG. 10, the damper assembly 220 is in communicationwith at least one controller 224 configured to receive information fromthe damper assembly 220 and provide information or control signals tothe damper assembly 220. For some embodiments, the controller 224 iscoupled to the damper assembly 220 through one or more conduits 222.Optionally, the controller 224 may be in communication with the damperassembly 220 using a wireless communication system, free spacecommunication systems, laser communication system, or the like. In theillustrated embodiment, the controller 224 comprises a stand-alonedevice coupled to the damper assembly 220 with the conduits 222.Optionally, the controller 224 may be coupled to the optical supportstructure 210 or integrally secured within a portion of the opticalsupport structure. During use, an embodiment of the controller 224receives vibrational information from at least one of the damperassemblies 220 and provides one or more signals to one or more damperassemblies 220 in communication with the optical support structure 210in a control loop configuration, thereby providing an active dampingarchitecture. Such vibrational information and signals may optionally becommunicated through the driver device 248 which may be disposed withinthe housing 250 or disposed in some other suitable location, includingnear or within the controller 224 itself.

Any suitable type of device or processor may be used as a controller224, including, without limitation, computers, micro-processors,integrated circuits devices, measuring devices, and the like.Optionally, the controller 224 may be in communication with one or moresensors 240 located within the damper assemblies 220 or coupled to theoptical support structure 210 at any location. In addition, controller224 may be coupled to a display 225 that may be used to display thestatus of the controller 224, vibration information from the sensors240, as well as allow interactive programming of the controller 224 toachieve a desired vibration damping result. The display 225 may be usedin conjunction with a computer or other processor (not shown) that maybe used to facilitate the display of information or interactiveprogramming of the controller 224.

FIGS. 12 and 13 show block diagrams illustrating method embodiments ofdamping vibration in an optical structure such as optical supportstructure 210. As shown in FIG. 12, an external excitation 270 isincident upon an optical support structure 272, which may be the same asor similar to optical support structure 210, and received by at leastone sensor 274 located therein or in communication therewith. In theillustrated embodiment, a first sensor 274A of a first actuator device(See FIG. 10) and a second sensor 274B of a second actuator device maybe used. The first sensor 274A and second sensor 274B may be integralwith the optical support structure 272. Also, the first sensor 274A andsecond sensor 274B may be positioned on the first surface 212. Note thatthe sensors 274 may be the same as or similar to the sensor 240discussed above. The first and second sensors 274A, 274B, respectively,generate and send a signal to a controller in the form of the signalconditioning and control electronics section 276, which is shown in moredetail in FIG. 13.

In some embodiments, the signal conditioning and control electronicssection 276 may include the driver device 248 (See FIG. 11) and/or thecontroller 224 (See FIG. 10), which processes the vibration signalinformation. As such, at least one driver device 248 (See FIG. 11)and/or the controller 224 (See FIG. 10) includes one or more algorithmsconfigured to generate a control signal to be transmitted to at leastone active element 278A or 278B of corresponding actuators, which may bethe same as or similar to the actuators 242 above, in communication withthe optical support structure 272. In some embodiments, the controlsignal may be tuned to drive the active elements 278A and 278B with anoptimal vibration-canceling output. As such, embodiments of the systemdisclosed herein enable a user to monitor the vibrational characteristicof a structure within an environment and provide an actively dampedarchitecture. For example, in some embodiments, the vibration damperassembly and controller system provides auto-ranging architecture whichutilizes a mean-square value of a feedback signal.

FIG. 12 shows an embodiment of a feedback or control loop schematic forthe control of damping systems used for reducing vibration of an opticalstructure. Although two sensors 274A and 274B and two active elements278A and 278B are shown, any number of sensors 274A, 274B and activeelements 278A, 278B may be used. The vibration damper system may beoperated in multiple-input-multiple-output (MIMO) format, where thesignal to each actuator 242 is derived from all the vibration sensors240. However, for some embodiments, it is useful for stability androbustness to operate the vibration damper system as a conglomeration ofseveral independent vibration damper devices or assemblies 220 eachhaving a respective sensor 240 and adjacent actuator 242. Each damperassembly 220 in such a system may be operated by a separate controlchannel of the controller 224. Embodiments of these control channels areshown in more detail in FIG. 13. The control functions include gainfactors K1 and K2 that define trade offs between damping performance andsystem stability. It may be useful, in some embodiments, to take thegain factors as high as possible for increasing damping power andthereby decreasing unwanted vibration of the optical support platform210 at a higher rate. However, in some cases, if the feedback gainfactors are too high, the system may become unstable. To determine fixedoptimal gain factors that include an acceptable stability safety marginwould normally require detailed knowledge of the complete mechanicalmodel of the plant or system including all resonant vibrational modes ofall components in combination. Even if such information were availableor readily discemable, the optimal gain factors may change over timebecause of variations in temperature, payload on the support structure210 etc. As such, methods and devices for adaptively tuning thevibration damping system are discussed below with regard to FIG. 14.

Referring to FIG. 13, an embodiment of a control channel pair for usewith an actively damped optical structure, such as optical supportstructure 210, is shown. As shown, a first pre-amplifier 300 of thesignal conditioning and control electronics section 276 receives aninput signal from the first sensor 274A. The first pre-amplifier 300processes the input signal and transmits a processed signal to a firstband-pass filter 302. Thereafter, the filtered signal is transmitted bythe first band-pass filter 302 to a first phase corrector 304.Thereafter, a first gain factor K₁ is applied to the phase correctedsignal. Thereafter, a gain factored signal is sent to a first filter anddriver 308 which processes the signal and drives the first activeelement 278A. In some embodiments, the first pre-amplifier 300, thefilter and driver 308 or both may be included in the driver unit 248discussed above. Similarly, the second pre-amplifier 302 of the signalconditioning and control electronics section 276 receives an inputsignal from the second sensor 274B. The second pre-amplifier 302processes the input signal and transmits a processed signal to a secondband-pass filter 322. Thereafter, the filtered signal is transmitted bythe second band-pass filter 322 to a second phase corrector 324, thephase correction step of which may be implemented by software processes.Thereafter, a second gain factor K₁ is applied to the phase correctedsignal as shown in box 326. The application of the second gain factor K₁may also be implemented by software processes. Thereafter, a gainfactored signal is sent to a second filter and driver 328 whichprocesses the signal and drives the second active element 278B. In someembodiments, the first pre-amplifier 302, the filter and driver 328 orboth may be included in the driver unit 248 discussed above. In someembodiments, any variety or combination of similar control architecturescould be used with the vibration damper assemblies 220 and controllers224.

These methods of producing a vibration suppression or damping signal tothe actuators 242 may also be adapted to work in a wide range ofpractical applications and diverse working environments. The practicallevels of environmental vibration encountered by optical supportstructures or platforms 210 can vary significantly, and variations ofthree orders of magnitude in vibration amplitude are not uncommon. Forsome environments, vibration variations may range from sub-micron persecond RMS amplitudes in quiet laboratories to significant fractions ofa millimeter per second RMS in commercial production facilities, such assemiconductor wafer production facilities. In order for the controller224 to maintain its vibration damping performance in conjunction withthe damper assembly 220 under these varied conditions, it must monitorthe vibration feedback signal from the vibration sensor 240 and maintainthe signal-to-noise ratio, phase, bandwidth as well as othercharacteristics of that signal as well as the same or similar propertiesof the control signal to the vibration damper assembly 220. Embodimentsof the controller 224 are configured to use a auto-ranging method thatutilizes the mean-square value of the vibration feedback signal from thesensor 240 in order to monitor the output amplitude of the vibrationsignal and adjust gain parameters as well as other factors in order tomaintain proper signal-to-noise ratio, phase, bandwidth as well as othercharacteristics. Other features of the vibration feedback signal fromthe sensor 240 may also be monitored, such as maxima and minima of thesignal.

For some embodiments, a method of automatically selecting an appropriaterange of input vibration signal detection in an active damper assembly,includes providing a vibration damper system having an active damperassembly 220 with a vibration sensor 240 and an actuator 242 andincluding a controller 224 coupled to both the sensor 240 and theactuator 242 by a control channel, such as the control channels shown inFIG. 13. The controller 224 may also have at least two vibrationfeedback signal inputs with gain factors appropriate to the signalstrength range for the vibration signal amplitude. The vibrationfeedback signal from the sensor 240 is monitored by the controller 224,and specifically, for some embodiments, the mean-square value of thevibration signal from the sensor 240 is monitored. The mean-square valueof the vibration feedback signal is then compared to a pre-selectedrange of signal values over a pre-selected period of time by thecontroller 224. If the monitored signal violates some desiredconstraints, such as being outside the pre-selected range of signalvalues, for a period of time, then a different and appropriate feedbacksignal range input is selected or switched to by the controller whichhas a gain factor appropriate for the mean-square value of the vibrationinput signal amplitude into the controller 224.

For example, if the vibration feedback signal, or mean-square valuethereof, has a value over a period of time that exceeds the pre-selectedrange of the selected feedback signal input of the controller 224, thecontroller 224 will switch the vibration feedback signal to a differentinput that may have a lower gain factor, so as not to over amplify thevibration feedback signal and avoid excessive noise or have to low asignal-to-noise ratio. In the alternative, if the vibration feedbacksignal, or mean-square value thereof, has a value over a period of timethat is below the pre-selected range of the selected feedback signalinput of the controller 224, the controller 224 will switch thevibration feedback signal to a different input that may have a highergain factor, so as not to under amplify the vibration feedback signal.In some cases, the pre-selected range in the lowest range gain factor ofsignal inputs of the controller 224 may still be violated, in which casea vibration overload condition may be said to exist. In such asituation, the controller 224 may present an error signal, such as avisual or audio signal, to the user of the system. In addition, thecontroller 224 may be configured to shut down the vibration dampingprocess in these circumstances. The overload condition may also bedetected with an error signal generated by a signal clipping detector ordetectors in the preamplifier.

Similar overload conditions may also be used to detect changes inpayload on the surface of the optical support platform 210 and makingadjustments, such as adjustments in the gain factors of the controlloops in response to the change in order to adapt thereto. Performanceof embodiments of the vibration damper system may need to be insensitiveto changes in payload properties or amounts on the surface or otherlocations of the optical support platform 210. The equipment positionedon the platform 210 may vary from lightweight to weights comparable tothe weight of the optical support platform 210 itself, or even greater.If the control loop gains K1 and K2 were tuned for a particular payloadconfiguration and if the payload is changed, there is potential for thecontroller 224 to become unstable. In such circumstances, the controller224 may be configured to identify the onset of instability and executesome instructions to remedy the situation or alert the user of thesituation. For example, the controller 224 may be configured to shutdown the control system or re-tune the control loop either with, orwithout user intervention.

An embodiment of a method of automatically adjusting gain factors in anactive damper system for changes in payload, may include providing avibration damper system including a vibration damper assembly or device220 with a vibration sensor 240 and an actuator 242 and including acontroller 224 coupled to both the sensor 240 and the actuator 242 by acontrol channel, such as the control channels in FIG. 13. The controller224 may have a vibration feedback signal input with gain factorsappropriate to the signal strength range for the vibration signal input.The vibration feedback signal from the vibration sensor 240 is monitoredfor vibration overload conditions. A vibration overload condition mayexist, as discussed above, when the pre-selected range in the lowestrange gain factor of signal inputs of the controller 224 are stillviolated. If a vibration overload condition exists, the controller 224,or rather the drive signal of the controller 224 to the actuator 242, isdisabled and a subsequent determination is made as to whether thevibration overload condition still exists. If the vibration overloadcondition ceases when the drive signal to the actuator 242 by thecontroller 224 is disabled, a change in payload on the optical supportplatform 210 has taken place. It may now be appropriate to recalibratethe gain factors in order to accommodate the change in payload.

FIG. 14 shows a graphical representation of a damping process which isspecifically configured to determine a gain factor or factors that willprovide good performance and vibration damping. In some embodiments, amethod of adaptively tuning the gain factors of the control channels ofthe controller 224 includes providing a vibration damper systemincluding one or more vibration damper devices with a vibration sensor274 and an active element 278 of an actuator 242 and including acontroller 224 coupled to both the sensor 274 and the active element 278by a control channel, such as the control channels shown in FIG. 13.Initially, all control channels except one active channel are disabledor shut down. In the remaining active control channel, the gain factoris increased until instability of the system is detected by thevibration sensor 274. The gain factor is then reduced by a smallincrement or increments in order to re-achieve system stability. Thehighest gain factor that achieved stability is then stored into a memoryunit, such as a non-volatile memory device.

An example of a non-volatile memory device may include an EEPROM memorychip. The procedure is then repeated for the remaining control channelswith all control channels being shut down except for the remainingactive control channel for which the gain factor will be optimized andstored. All control channels are then activated and the gain factors toeach control channel increased in an amount proportional orsubstantially proportional to the stored gain values for each respectivechannel. The gain factors of each control channel are proportionallyincreased until instability of the vibration damper system is againdetected by the controller 224 by monitoring the vibration feedbacksignal or signals from the vibration sensor or sensors 274. The gainfactors are then reduced in small steps for all control channels untilstability is achieved for the vibration damper system. For someembodiments, gain factors for each control channel are reduced in smallsteps proportional to the stored gain factor simultaneously to regainstability if necessary. While the controller 224 is reducing the gainfactor of a control channel in order to re-achieve stability of thesystem, a variety of approaches may be used to expedite thedetermination of the acceptable gain factor. For example, in oneembodiment, the determination of the maximum gain factor that willproduce a stable system or system component is carried out by aconverging search method. In some cases the converging search includes abisection method. In addition, it may be desirable after a gain factorhas been reduced to achieve stability, to further apply a safety factorreduction to each of the gain factor values. The safety factor reductionmay be about 5 percent to about 50 percent of the base gain factor. Inother embodiments, other monotonous functions of gain values may be usedinstead of direct proportionality to increase or reduce the gain valuesin each control channel, such as power laws, exponential laws orlogarithmic laws.

FIGS. 15A-15C illustrate various screen displays on the display 225 ofthe controller 224 which is coupled to two vibration damper assemblies220. A similar display may be used for any number of controllers 224 orvibration damper assemblies 220, or components thereof. FIG. 15A shows ascreen shot of the display 225 while the controller is in an “auto tune”tab. The display shows the status of some of the controller settings anda dual channel graphical display of vibration amplitude as measured bythe two vibration sensors 274A, 274B versus frequency of the vibration;the graphs obtained with damping disabled and enabled are superimposedfor comparison. FIG. 15B shows the “auto tune” tab with a single channeldisplay of vibration amplitude versus vibration frequency of vibrationsignals obtained with damping disabled and enabled superimposed on eachother for comparison. FIG. 15C shows a screen shot of the display 225 ofthe controller with the controller disposed in “manual tune” mode ortab. This tab provides direct control over the gain factors of therespective control loops of the damper assemblies 220. Both of thedisplay tabs display the gain factor for each control loop, thefrequency of a notch filter which may optionally be enabled. The statusof active damping, whether enabled or disabled is shown along with amenu to make the selection between the two. The graphical display in theright hand portion of the display may be configured to show an undampedvibration signal and a damped vibration signal. It may also beconfigured to show a signal in either frequency domain or time domain.

Referring again to FIG. 15A, the various interactive display “buttons”may be selected to display or activate certain features. For example,clicking on “Enable Damping” or “Disable Damping” buttons will enable ordisable active damping by the system. If damping is enabled, the“Disable Damping” button is visible, and vice versa. By clicking on the“Measure Undamped Vibration Level” button, the vibration level will berecorded and displayed with the active damping by the active elements278 of actuators 242 disabled. The vibration data may be averaged overseveral time frames and the number of time frames for averaging may beselected by the user in the “Options” tab. By clicking on the “MeasureDamped Vibration Level” button, the damped vibration level will berecorded and displayed. The data may be averaged over a similar timeperiod to that of the undamped vibration level and may also be averagedover several time frames. Both the damped and undamped vibration levelsmay be displayed in either frequency domain or time domain by selectingeither “FFT” or “Time Response” from the pull down menu on the display.The FFT display resolution may be about 0.5 Hz to about 5 Hz. Theselection between single channel or dual channel display of vibrationlevels may be made by selecting the “Show Graph” button. The “Save Data”button may be activated to save the displayed data. If the “HTML” optionis selected in the “Options” tab, all graphs are saved in HTML fileformat. If the “Text” file option is selected in the “Options” tab, themeasured data will be saved in two text files. The first file is used tostore time response data and the second file is used to store frequencyresponse data.

FIGS. 16 and 17 show an alternate embodiment of an optical structure inthe form of an optical component 400 that includes a vibration damperassembly 220 such as the vibration damper 220 shown in FIG. 11. Asshown, the optical component 400 in the form of a vertical post mountincludes a body portion 402 having a vibration damping device orassembly 220 coupled thereto or disposed therein within a damper section404 of the body portion 402. The body portion 402 has an upper end 401and a lower end 403. In some embodiments, the body portion 402 may havea mount plate 405 secured to the lower end 403 of the body portion 402.The mount plate 405 may be configured to be secured or coupled toanother optical support structure or platform, such as an optical table,bench, fixture, or the like using any number of attachment methods,including, without limitation, mechanical attachment, magneticattachment, adhesive attachment, welded attachment, detachablyattachment techniques, and non-detachable attachment methodologies. Anoptical mount device in the form of a lens holder 406 is secured to amount plate 407 disposed on the upper end 401 of the body portion 402.

Embodiments of the mount plate 407 may be detachably secured to theupper end 401 of the body portion 402 or, in other embodiments,permanently secured thereto. The mount plate 407 has a mount surface orstructure (not shown) that may allow standard optical mount components,such as lens holders, laser mounts, and the like, to be detachablysecured to the mount plate 407. In this way, optical mount componentsmay be mounted directly to an optical support structure that has anactive vibration damper device or assembly integrally mounted thereon orcoupled thereto. Such an active vibration damper assembly may be tunedspecifically to the resonant frequencies and frequency ranges of theoptical component 400, which may differ from the resonant vibrationalfrequencies and frequency ranges of the underlying table or platform,such as the optical substrate 210, as shown in FIG. 10, to which theoptical component 400 may be mounted.

The body section 402 may include one or more vibration sensors 240disposed therein and one or more active vibration actuators 242 havingone or more active elements therein. A driver 248 may be coupled to thevibration sensor 240 and actuator 242. In essence, one or moreembodiments of the vibration damper assemblies 220 (not shown),discussed above, may be integrated into the body portion 402 of theoptical component 400. As such, the vibration damper assembly isindirectly mechanically coupled to the optical mount device or lensholder 406 and may be used to suppress or cancel mechanical vibration ofthe optical mount device 406.

At least one controller 424 may be coupled to the vibration damperassembly 220 disposed within the body section 402 by conduits 414.Optionally, the controller 424 may be in wireless communication with thevibration damper assembly 220 disposed within the damper section 404. Inalternate embodiments, at least one controller 424 may be positionedwithin the body portion 402. Embodiments of the controller 424 mayoperate in a manner the same as, or similar to, the manner of operationof the controllers 224, 106 and 64 discussed above. In addition,controller 424 may be coupled to a display 426 that may be used todisplay the status of the controller, vibration information from thesensor 240, as well as allow interactive programming of the controller424 to achieve a desired vibration dampening result.

In the illustrated embodiment, the mount device 406 includes an opticmount device in the form of a lens support or mount. Optionally, themount device 406 may comprise any variety of optical component mounts,supports, posts, rods, translation stages, stages, plates, and the like.In some embodiments, the optical component 400 is positioned within anoptical component itself. For example, the optical component 400 may bepositioned within a housing of a laser system thereby reducing oreliminating the effects of vibration therefrom. Further, the opticalcomponent 400 may be used to support any variety of vibration sensitiveequipment in any variety of environments. For example, the opticalcomponent 400 may be secured or coupled to a support device used tosupport a spectral analyzer within the fuselage of an aircraft or avariety of other applications. In some embodiments, the body portion 402of the optical component 400 may be made from materials such asaluminum, cast iron, carbon fiber, glass filled polymer or the like.

With regard to the above detailed description, like reference numeralsused therein refer to like elements that may have the same or similardimensions, materials and configurations. While particular forms ofembodiments have been illustrated and described, it will be apparentthat various modifications can be made without departing from the spiritand scope of the embodiments of the invention. Accordingly, it is notintended that the invention be limited by the forgoing detaileddescription.

1. A method of adaptively tuning a controller of an active vibrationdamper system, comprising providing a vibration damper system for anoptical structure including at least one vibration damper assembly witha vibration sensor and an actuator and including a controller coupled toboth the sensor and the actuator by a control channel; disabling allcontrol channels except one active channel; in the remaining controlchannel, increasing the gain factor until instability in the vibrationdamper system is detected by the vibration sensor; reducing the gainfactor by a small increment to re-achieve stability; storing the gainfactor that achieved stability; repeating the procedure for anyremaining control channels; activating all control channels andincreasing gains to each control channel in an amount proportional tothe stored gain value for each respective channel until instability isagain detected by the vibration sensor; and reducing the gain factor insmall steps for each control channel until stability is achieved for thevibration damper system.
 2. The method of claim 1 further comprisingreducing gain factors for each control channel in small stepsproportional to the stored gain factor simultaneously to regainstability if necessary.
 3. The method of claim 1 wherein the reductionof the gain factor is carried out by a converging search.
 4. The methodof claim 3 wherein the converging search comprises a bisection.
 5. Themethod of claim 2 wherein the reduction of the gain factor is carriedout by means of a converging search.
 6. The method of claim 5 whereinthe converging search comprises a bisection.
 7. The method of claim 1further comprising applying a safety factor reduction to each of thegain factor values.
 8. A method of automatically selecting anappropriate range of input vibration signal detection in an activedamper device, comprising: providing a vibration damper system for anoptical structure including a vibration sensor and an actuator andincluding a controller coupled to both the sensor and the actuator by acontrol channel and having at least one vibration feedback signal inputwith gain factors appropriate to the signal strength range for theinputs; monitoring the vibration feedback signal from the vibrationsensor; comparing the vibration feedback signal to a pre-selected rangeof signal values over a pre-selected period of time; selecting anappropriate feedback signal range input with an appropriate gain factorfor the input signal amplitude in the controller.
 9. The method of claim8 wherein the vibration damper input signal is switched to a lower gainvibration feedback signal input if the input signal was too high for thepre-selected range.
 10. The method of claim 8 wherein the vibrationdamper input signal is switched to a higher gain vibration feedbacksignal input if the input signal was too low for the pre-selected range.11. The method of claim 8 further comprising monitoring the vibrationfeedback signal and switching the feedback signal to a signal input withthe lowest gain factor; detecting a signal amplitude that is still outthe acceptable range of input amplitudes; and determining that avibration overload condition exists for the active damper system. 12.The method of claim 11 wherein the controller is configured to generatean error signal when an overload condition exists and further comprisinggenerating an error signal.
 13. The method of claim 12 wherein thegeneration of an error signal comprises generating a visual errorsignal.
 14. The method of claim 1 wherein monitoring the vibrationfeedback signal from the vibration sensor comprises monitoring themean-square value of the vibration feedback signal.
 15. A method ofdetermining a payload change in an active damper system coupled to anoptical structure, comprising: providing an active vibration dampersystem including a vibration sensor and an actuator and including acontroller coupled to both the sensor and the actuator by a controlchannel and having a vibration feedback signal input with gain factorappropriate to the signal strength range for the vibration signal input;monitoring the vibration feedback signal for vibration overloadconditions; detecting a vibration overload condition, disabling thedrive signal to the actuator from the controller; and determiningwhether the vibration overload condition still exists.
 16. The method ofclaim 15 wherein a determination of payload change is indicated by thecontroller to a user when the overload condition ceases to exist afterthe drive signal to the actuator from the controller is disabled.
 17. Anoptical table with active vibration damping, comprising: an opticalmount surface, an active vibration damper system which includes anactive vibration damper assembly having a vibration sensor and actuatorwhich are mechanically coupled to the optical mount surface and acontroller in communication with the vibration sensor and actuator. 18.The optical table of claim 17 wherein the vibration sensor and actuatorare coupled directly to the optical mount surface.
 19. The optical tableof claim 18 wherein the vibration sensor and actuator of the vibrationdamper assembly are disposed within a single housing.
 20. An opticalcomponent with active vibration damping, comprising: a body portion, amount plate secured to the body portion and configured to be mounted toan optical mount surface, and an actuator including an active elementcoupled to a mass and a flexure mechanically coupled to the bodyportion.
 21. The optical component of claim 20 further comprising avibration sensor mechanically coupled to the body portion.
 22. Theoptical component of claim 21 wherein the vibration sensor and actuatorare disposed within a single housing.
 23. The optical component of claim21 further comprising a controller in communication with the actuatorand the vibration sensor.
 24. The optical component of claim 20 whereinthe body portion comprises an optical post mount.
 25. The opticalcomponent of claim 24 further comprising an optic mount device securedto the body portion and configured to receive an optic.
 26. The opticalcomponent of claim 25 wherein the optic mount device is configured toreceive a lens.
 27. The optical component of claim 24 wherein the bodyportion comprises aluminum.
 28. The optical component of claim 24wherein the body portion comprises glass filled polymer.
 29. The opticalcomponent of claim 20 wherein the mount plate comprises aperturesconfigured to mate with threaded apertures of a desired optical mountsurface.
 30. An optical component with active vibration damping,comprising: a body portion, a mount plate secured to the body portionand configured to be mounted to an optical mount surface, and an activedamper assembly coupled to the body portion including a vibration sensorand an actuator having an active element coupled to a mass and a flexure31. The optical component of claim 30 wherein the vibration sensor andactuator are disposed within a single housing.
 32. The optical componentof claim 31 further comprising a controller in communication with theactive damper assembly.